linux-kernel - Re: [PATCH 1/2] dt-bindings: phy: Add Qualcomm Synopsys High-Speed USB PHY binding

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Message-ID: <20181119065503.GB10788@dragon>
Date:   Mon, 19 Nov 2018 14:55:06 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Sriharsha Allenki <sallenki@...eaurora.org>,
        Anu Ramanathan <anur@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vinod <vkoul@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: phy: Add Qualcomm Synopsys High-Speed
 USB PHY binding

On Sat, Nov 17, 2018 at 09:13:38AM -0600, Rob Herring wrote:
<snip>
> > > > +- qcom,init-seq:
> > > > +    Value type: <u32 array>
> > > > +    Definition: Should contain a sequence of <offset value delay> tuples to
> > > > +                program 'value' into phy register at 'offset' with 'delay'
> > > > +           in us afterwards.
> > >
> > > If we wanted this type of thing in DT, we'd have a generic binding (or
> > > forth).
> >
> > Right now, this is a qualcomm usb phy specific bindings - first used in
> > qcom,usb-hs-phy.txt and I extended it a bit for my phy.  As this is not
> > a so good hardware description, I'm a little hesitated to make it
> > generic for other platforms to use in general.  What about we put off it
> > a little bit until we see more platforms need the same thing?
> 
> I'm not saying I want it generic. Quite the opposite. I don't think we
> should have it either generically or vendor specific. The main thing I
> have a problem with is the timing information because then we're more
> that just data. Without that we're talking about a bunch of properties
> for register fields or just raw register values in DT. That becomes
> more of a judgement call. There's not too much value in making a
> driver translate a bunch of properties just to stuff them into
> registers on init. But then just allowing any raw register value to be
> in DT could be easily abused.

Rob,

I agree with your comments.  Honestly, I'm not comfortable with this
'qcom,init-seq' thing in the first impression.  The similar existence in
mainline qcom,usb-hs-phy.txt makes me think it might be acceptable with
the timing data added.  Okay, I know your position on this now.

@Sriharsha,

Seeing that 'qcom,init-seq' is being configured with the exactly same
values for both HS phys in SoC level dts file (qcs404.dtsi), I think
such settings can be moved into driver code as SoC specific data.
Unless you have a different view on this, I will do it with v4.

Shawn